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This research focuses on the development of a state observer for performing indirect measurements of the main variables involved in the soybean oil transesterification reaction with a guishe biochar-based heterogeneous catalyst; the studied reaction takes place in a batch reactor. The mathematical model required for the observer design includes the triglycerides' conversion rate, and the reaction temperature. Since these variables are represented by nonlinear differential equations, the model is linearized around an operation point; after that, the pole placement and linear quadratic regulator (LQR) methods are considered for calculating the observer gain vector L(x). Then, the estimation of the conversion rate and the reaction temperature provided by the observer are used to indirectly measure other variables such as esters, alcohol, and byproducts. The observer performance is evaluated with three error indexes considering initial condition variations up to 30%. With both methods, a fast convergence (less than 3 h in the worst case) of the observer is remarked.

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Antibiotics in wastewater treatment plants can alter the physiological activity and the structure of microbial communities through toxic and inhibitory effects. Physiological adaptation, kinetic, and population dynamics behavior of a nitrifying sludge was evaluated in a sequential batch reactor (SBR) fed with 14.4 mg/L of ampicillin (AMP). The addition of AMP did not affect ammonium consumption (100 mg NH4+-N/L) but provoked nitrite accumulation (0.90 mg NO2--N formed/mg NH4+-N consumed) and an inhibition of up to 67% on the nitrite oxidizing process. After 30 cycles under AMP feeding, the sludge recovered its nitrite oxidizing activity with a high nitrate yield (YNO3-) of 0.87 ± 0.10 mg NO3--N formed/mg NH4+-N consumed, carrying out again a stable and complete nitrifying process. Increases in specific rate of nitrate production (qNO3-) showed the physiological adaptation of the nitrite oxidizing bacteria to AMP inhibition. Ampicillin was totally removed since the first cycle of addition. Exposure to AMP had effects on the abundance of bacterial populations, promoting adaptation of the nitrifying sludge to the presence of the antibiotic and its consumption. Nitrosomonas and Nitrosospira always remained within the dominant genera, keeping the ammonium oxidizing process stable while an increase in Nitrospira abundance was observed, recovering the stability of the nitrite oxidizing process. Burkholderia, Pseudomonas, and Thauera might be some of the heterotrophic bacteria involved in AMP consumption.

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Se evaluó la biodegradación de polietilenglicol de peso molecular 400 - PEG 400 con el consorcio Pseudomonas sp. y Rhizobium trifolii en reactores en Batch; para determinar las condiciones óptimas de operación del reactor se preparó medio con sales mínimas esenciales suplementado con peptonaCSMEP; en estos medios se estimó el comportamiento del consorcio con condiciones de temperatura entre 15-37°C, pH en un rango de 5-9 y concentración de PEG 400 del .1-2%. Con los resultados obtenidos en estos ensayos previos se ensamblaron tres reactores en Batch - BK. Se analizaron 14 muestras del contenido de cada uno de los reactores durante 20 días para medir la biodegradación del PEG 400 usando demanda química de oxígeno - DQO en sistema de digestión cerrado. Se obtuvo una disminución de hasta el 98.5% del poliéter, lo que mostró que la simbiosis fue efectiva para alcanzar una remoción importante del contaminante.

The biodegradation of polyethylene glycol of molecular weight 400 - PEG 400 was evaluated with the consortium Pseudomonas sp. and Rhizobium trifolii in Batch reactors. To determine the optimal operating conditions of the reactor, a medium with minimum essential salts supplemented with CSMEP peptone was prepared; In these media, the behavior of the consortium was estimated with temperature conditions between 15-37°C, pH in a range of 5-9 and PEG 400 concentration of .1-2%. With the results obtained in these previous tests, three Batch - BK reactors were assembled. 14 samples of the contents of each one of the reactors were analyzed during 20 days to measure the biodegradation of PEG 400 using chemical oxygen demand - COD in a closed digestion system. A decrease of up to 98.5% of the polyether was obtained, which showed that the symbiosis was effective to achieve an important removal of the contaminant.

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The kinetic model derived in this study was able to adequately predict the simultaneous oxidation of ammonia, nitrite, and m-cresol and microbial growth using nitrifying sludge in a sequencing batch reactor. Time-varying inhibition and inactivation effects were successfully incorporated in the process kinetics to account for the past cell exposure history to m-cresol increasing concentrations (up to 150 mg C L-1). The initial concentration of the microbial species (ammonia and nitrite oxidizers, heterotrophs) was evaluated using pyrosequencing of DNA samples of the consortium. These measurements allowed to establish a model that explicitly handles specific reaction rates and to enhance the practical identifiability of the model parameters. A single simulation run was used to adequately predict the kinetic behavior of the main variables throughout the 242 cycles using a single set of initial conditions in the first cycle. This kind of dynamic model may be used as a helpful predictive tool to improve nitrification by avoiding the occurrence of severely repetitive inhibitive conditions due to the presence of inhibitive/toxic aromatic compounds.

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Production, preservation and recovery of sludge with stabilized nitrifying activity over long time can be difficult. Information on the ability of nitrifying sludge to regain its nitrifying activity after long-term storage is still scarce. In this work, the physiological and kinetic changes during the reactivation and stabilization of a nitrifying sludge previously exposed to ampicillin (AMP) were evaluated in a sequential batch reactor (SBR) after its long-term storage (1 year) at 4 °C. After storage, both ammonium and nitrite oxidizing processes were slow, being nitrite oxidation the most affected step. During the reactivation stage (cycles 1-6), physiological and kinetic activity of the nitrifying sludge improved through the operating cycles, in both its ammonium oxidizing and nitrite oxidizing processes. At the end of the reactivation stage, complete nitrifying activity was achieved in 10 h, reaching ammonium consumption efficiencies (ENH4 +) close to 100% and nitrate yields (YNO3 -) of 0.98 mg NO3 --N/mg NH4 +-N consumed without nitrite accumulation. During the stabilization stage (cycles 7-17), results indicated that the sludge could maintain a steady-state respiratory process with restoration percentages of 100% for nitrifying specific rates (qNH4 + and qNO3 -) with respect to their values obtained before storage. Furthermore, during the addition of 15 mg AMP/L (cycles 18-21), the sludge preserved its metabolic capacity to biodegrade 90% of AMP in 2 h. Therefore, long-term storage of nitrifying sludge could be used to preserve nitrifying inocula as bioseeds for bioremediation and bioaugmentation strategies.

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The nutrient biological removal from sewage, especially from anaerobic reactor effluents, still represents a major challenge in conventional sewage treatment plants. In this work, the nitrogen and phosphorus removal from anaerobic pre-treated domestic sewage in an up-flow anaerobic sludge blanket (UASB) reactor was assessed in a structured fixed bed reactor (SFBR) operated in a continuous and in a batch mode using polyurethane foam as material support for biomass and fermented glycerol as the exogenous carbon source. The SFBR was operated as a sequencing batch reactor with cycles of 90, 120, and 150 min under anaerobic, oxic, and anoxic conditions, respectively, reaching average efficiencies for total nitrogen and phosphorus removal of 88% and 56%, respectively. Fermented glycerol was added during the non-aerated periods. Under continuous feeding, the SFBR was operated with aeration/non-aeration periods of 2/1 (h) and 3/1 (h), hydraulic retention time of 12 h, and a recirculation ratio of 3. Without fermented glycerol addition, the maximum removal of total nitrogen (TN) reached 42%, while adding glycerol in the non-aerated period improved TN removal to 64.9% (2/1 h) and 69.5% (3/1 h). During continuous operation, no phosphorus removal was observed, which was released during the non-aerated period, remaining in the effluent. Optical microscopy analyses confirmed the presence of polyphosphate granules and of the phosphorus accumulating organisms in the reactor biofilm. It was concluded that the batch feeding method was determinant for phosphorus removal. The structured fixed bed reactor with polyurethane foam proved to be feasible in the removal of organic matter and nutrients remaining in the UASB reactor effluent.

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The presence of colonial and solitary ciliated peritrichous protozoa was determined in a Sequencing Batch Reactor system filled with tezontle, a volcanic rock, economic, and abundant material that can be found in some parts of the world, like Mexico. The presence of these protozoa was related to the removal efficiencies of organic matter. Also, two novel staining techniques are proposed for staining both colonial and solitary peritrichous protozoa. The results show that tezontle promotes the growth of solitary and colonial ciliated peritrichous protozoa, which, once identified, could be used as indicators of the efficiency of the wastewater treatment process. Additionally, the staining techniques established in the current study allowed the precise observation of protozoan nuclei. They can represent a useful complementary methodology for identifying protozoan species present in water treatment processes, along with the already existing identification techniques. The number and variety of protozoa found in the system may be considered potential bioindicators of water quality during biological treatments.

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This paper proposes and develops a protocol for measuring the aerobic granulation potential of sludge, aiming to provide an affordable and simple alternative that can facilitate the development of aerobic granulation technology. In this sense, the protocol comprises a set of parameters and considerations that interact to create a controlled environment and stimulate cell population clustering. All of this is done in the context of procedural simplicity, low cost, and the speed at which results are obtained. The protocol is essentially a three-stage method: preparation of the substrate, adaptation of the inoculum, and implementation of the protocol. Simple parameters were measured to evaluate the granulation process: SVI, settling velocity, and morphological parameters. The protocol was validated according to optimal ranges and criteria previously established in the literature. For this purpose, an activated sludge inoculum from a domestic wastewater treatment plant was submitted to the protocol, obtaining an optimal response of the biomass (SVI5 =13.90 mL g-1, settling velocity= 25,79 m h-1, Diameter > 0.2 mm) in a relatively short time (7 d). The results show that this protocol can constitute a tool for evaluation and decision-making using traditional laboratory equipment and is applicable at different scales.

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RESUMO Neste estudo, foram obtidas as cinéticas e isotermas de adsorção do fenol presentes em efluentes sintéticos em reator batelada e coluna de leito fixo, utilizando como adsorvente carvão ativado de casca de coco. O objetivo foi a obtenção dos parâmetros cinéticos e de equilíbrio do processo para simular diferentes condições operacionais em uma coluna de adsorção em leito fixo. Foram avaliadas a influência do pH, a massa de adsorvente, a concentração inicial de fenol e três diferentes temperaturas para os testes em reator batelada. Foi possível trabalhar no pH natural da solução e o aumento da temperatura indicou adsorção exotérmica, favorável e espontânea. Os dois modelos de isoterma (Langmuir e Freundlich) representaram bem os dados experimentais (R2 ≈ 0,9). Valores aproximados de capacidade máxima de adsorção foram encontrados para o reator batelada e para a coluna de leito fixo (qmáx = 41,69 mg.g-1 para o reator batelada e qmáx = 41,98 mg.g-1 para a coluna de leito fixo). O método de Volumes Finitos foi utilizado na discretização das equações matemáticas e um algoritmo computacional foi implementado em linguagem FORTRAN. O código computacional foi validado com dados experimentais deste trabalho (erro médio de 13%), podendo-se assim simular diferentes condições operacionais do sistema de adsorção em coluna de leito fixo com vista a futuras aplicações industriais.

ABSTRACT In this study, the kinetics and adsorption isotherms of phenol present in synthetic effluents were obtained in a batch reactor and fixed bed column, using adsorbent coconut shell activated carbon. The objective was to obtain the kinetic and equilibrium parameters of the process to simulate different operating conditions in a fixed bed adsorption column. The influence of the pH, adsorbent mass, initial phenol concentration, and three different temperatures for the batch reactor tests were evaluated. It was possible to work on the natural pH of the solution and the temperature increase indicated exothermic, favorable, and spontaneous adsorption. Both isotherm models (Langmuir and Freundlich) represented the experimental data (R2 ≈ 0.9). Approximate values of maximum adsorption capacity were found for the batch reactor and for the fixed bed column (qmax = 41.69 mg g-1 for the batch reactor and qmax = 41.98 mg g-1 for the fixed bed column). The Finite Volume method was used in the discretization of the mathematical equations and a computational algorithm was implemented in FORTRAN programming language. The computational code was validated with experimental data of this work (mean error of 13%) and it was possible to simulate different operational conditions of the fixed bed column adsorption system for future industrial applications.

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The increasing use of chemical fertilizers causes the loss of natural biological nitrogen fixation in soils, water eutrophication and emits more than 300 Mton CO2 per year. It also limits the success of external bacterial inoculation in the soil. Nitrogen fixing bacteria can be inhibited by the presence of ammonia as its presence can inhibit biological nitrogen fixation. Two aerobic sludges from wastewater treatment plants (WWTP) were exposed to high ammonium salts concentrations (>450 mg L-1 and >2 dS m-1). Microbial analysis after treatment through 16S pyrosequencing showed the presence of Fluviicola sp. (17.70%), a genus of the Clostridiaceae family (11.17%), and Azospirillum sp. (10.42%), which were present at the beginning with lower abundance. Denaturing gradient gel electrophoresis (DGGE) analysis based on nifH genes did not show changes in the nitrogen-fixing population. Nitrogen-Fixing Bacteria (NFB) were identified and associated with other microorganisms involved in the nitrogen cycle, presumably for survival at extreme conditions. The potential use of aerobic sludges enriched with NFB is proposed as an alternative to chemical fertilizer as this bacteria could supplement nitrogen to the plant showing competitive results with chemical fertilization.

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This study investigated the effect of magnetite nanoparticles (Np-magnetite) added to a pilot-scale sequencing batch reactor (SBR) treating domestic wastewater, to improve aerobic granular sludge (AGS) formation and the effects of granule disintegration. Np-magnetite additions (75 mg L-1) were made during the start-up of the reactor and repeated after 100 and 170 days, when granule disintegration was observed. From the first Np-magnetite addition, SVI5 was reduced from 1315 to 85 mL g-1. The granular biomass was observed on the 56th day, when 57% of the granules presented diameters bigger than 212 µm. The 100-day disintegration episode disturbed the granular biomass, reducing the volatile suspended solids by 51%, increasing the SVI values to above 200 mL g-1. Np-magnetite addition recovered all the granular biomass parameters to the values observed before disintegration. The treatment efficiency was stable during operation of the reactor for nutrients (52.8 ± 23.4% NH4+-N; 54.5 ± 12.2% PO43--P) and carbonaceous organic matter (71.7 ± 12.7% BOD5; 77.5 ± 10.0% CODt). Np-magnetite addition changed the microbial community of the granular sludge, analysed via high-throughput 16S RNA sequencing, and recovered the treatment efficiency previously disturbed by the disintegration processes. These results indicate the potential of Np-magnetite as an agent for sludge aggregation in an aerobic granular reactor.

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Aerobic granular sludge (AGS) has been considered a breakthrough in the wastewater treatment sector given its key characteristics, such as excellent settleability, simultaneous removal of organic and nutrient pollutants, and compactness. However, the formation of granules often delays the start-up of granular-based systems, especially in large-scale settings. This study addressed the start-up of a pilot-scale AGS sequencing batch reactor (SBR) treating domestic sewage, monitored for over 280 days. The challenges faced during aerobic granulation using a mixture of activated sludge and anaerobic granular sludge as inoculum and the performance of the reactor on organic matter, nitrogen, and phosphorus removal were discussed. Results showed that robust and stable granules were formed after an initial period of around six months, with the settling time playing a key role on granules development. At least 80% of granules had a diameter greater than 0.2 mm and 60% >1 mm. In general, the reactor achieved high nitrogen removal efficiency, as well as satisfactory removal of soluble COD. However, total COD abatement was impaired by the various episodes of suspended solids loss with the effluent. Overall, this study demonstrated that the reactor was efficient in the treatment of domestic sewage, but its performance was adversely affected from sudden changes in the influent quality. PRACTITIONER POINTS: Aerobic granular sludge (AGS) applied to small-scale domestic sewage treatment. The control of sludge age in AGS can be a problem due to short sedimentation times. High DO to maintain aerobic granulation can economically make the process economically unfeasible in tropical countries. A sludge with excellent sedimentation properties was obtained. However, maintaining the granule over time is a challenge.

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A kinetic study was carried out in a sequencing batch reactor (SBR) (125 mg NH4+-N/L) inoculated with a physiologically stable nitrifying sludge not previously acclimated to sulfur compounds and fed at different initial sulfide concentrations (2.5-20.0 mg HS--S/L). Up to 10.0 mg HS--S/L, the nitrifying process kept stable and complete, reaching an ammonium consumption efficiency (ENH4+) of 100% and a nitrate yield (YNO3-) of 0.95 ± 0.03 mg NO3--N/mg NH4+-N consumed. At 15.0 and 20.0 mg HS--S/L, after an initial alteration in the nitrite oxidizing process, the YNO2- was decreasing throughout the cycles and the YNO3- increasing, obtaining in the last cycle at 20.0 mg HS--S/L, an ENH4+ of 100%, a YNO2- of zero, and a YNO3- of 0.80 mg NO3--N/mg NH4+-N consumed. At the end of the period at 20.0 mg HS--S/L, the specific rates of ammonium consumption and nitrate formation were 15 and 55% lower than their respective values in the control period without sulfide addition, showing that the sludge had a better metabolic adaptation for ammonium oxidizing activity than for nitrite oxidizing activity. The sludge acquired a higher sulfide oxidation capacity along the cycles. Bacterial population dynamics assessment indicated that the ammonium oxidizing bacteria (AOB) community was more diverse and stable than the nitrite oxidizing bacteria (NOB) community. The use of consortia with a previously stabilized nitrifying activity in SBR may constitute an alternative for eliminating simultaneously ammonium by nitrification and sulfide by sulfide oxidation and be implemented for the treatment of wastewater with ammonium and sulfide.

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Microorganisms in aerobic granules formed in sequencing batch reactors (SBR) remove contaminants, such as xenobiotics or dyes, from wastewater. The granules, however, are not stable over time, decreasing the removal of the pollutant. A better understanding of the granule formation and the dynamics of the microorganisms involved will help to optimize the removal of contaminants from wastewater in a SBR. Sequencing the 16S rRNA gene and internal transcribed spacer PCR amplicons revealed that during the acclimation phase the relative abundance of Acinetobacter reached 70.8%. At the start of the granulation phase the relative abundance of Agrobacterium reached 35.9% and that of Dipodascus 89.7% during the mature granule phase. Fluffy granules were detected on day 43. The granules with filamentous overgrowth were not stable and they lysed on day 46 resulting in biomass wash-out. It was found that the reactor operation strategy resulted in stable aerobic granules for 46 days. As the reactor operations remained the same from the mature granule phase to the end of the experiment, the disintegration of the granules after day 46 was due to changes in the microbial community structure and not by the reactor operation.

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The metabolic and kinetic behaviour of a nitrification process in the presence of 2-chlorophenol (2-CP) was evaluated in two sequencing batch reactors (SBR1, SBR2) inoculated with nitrifying sludge previously exposed to phenolic compounds. The SBR1 was inoculated with sludge previously exposed to 2-CP, while the SBR2 was inoculated with sludge previously exposed to p-cresol. An inhibitory effect of 20 mg 2-CP-C/L on both nitrification processes was observed, as specific rates decreased according to a control assay in the absence of 2-CP. However, the inhibitory effect decreased throughout the cycles. At the end of cycle 6, a stable nitrifying process was observed with the sludge previously exposed to 2-CP (SBR1), as an ammonium consumption efficiency and a nitrate production yield close to 99.6 ± 0.3% and 0.99 ± 0.02 were respectively achieved. Despite a complete ammonium consumption being achieved with the sludge previously exposed to p-cresol (SBR2), partial nitrification was observed as nitrate production yield accounted for 0.28 ± 0.08 and nitrite was accumulated within the culture. Nevertheless, both nitrifying sludges had the ability to completely consume 2-CP. The use of SBR systems with nitrifying sludge previously exposed to 2-CP resulted in a better nitrification performance, thus it may be a good alternative for achieving a stable nitrifying respiratory process where complete and simultaneous ammonium and 2-CP consumption can be acquired.

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RESUMO Os reatores operados em bateladas sequenciais (RBS) com biomassa granular aeróbia são uma tecnologia compacta e promissora no tratamento de águas residuárias. Porém, sua utilização com esgoto sanitário ainda é um desafio, devido à instabilidade e desintegração dos agregados. O presente trabalho avaliou a granulação da biomassa em um RBS em escala piloto, sem a adição de inóculo, para o tratamento de esgoto sanitário. O estudo foi dividido em três estratégias operacionais com ciclos compostos pelas fases: enchimento, anóxica, aeróbia, sedimentação, descarte e repouso. Trabalhou-se com variações no tempo dos ciclos, 4 horas (estratégias I e II) e 6 horas (estratégia III), e na fase anóxica, 13, 30 e 90 minutos nas estratégias I, II e III, respectivamente. O desenvolvimento dos grânulos ocorreu de forma natural, sem inoculação, e o reator tratou o esgoto sanitário atendendo às exigências nacionais de padrões de lançamento de efluentes. As características do lodo granular aeróbio e o desempenho do reator no tratamento de esgoto melhoraram com o aumento da fase anóxica. Grânulos (200 a 400 µm) compreenderam mais de 80% da biomassa com boas características de sedimentabilidade (a razão entre os índices volumétricos de lodo após 30 e 10 minutos de sedimentação - IVL30/IVL10 - esteve entre 0,7 e 1,0) na estratégia III. As variáveis de maior relevância no processo foram a razão IVL30/IVL10 e a razão entre a demanda química de oxigênio solúvel do efluente e do anóxico (DQOS efluente/DQOS anóxico), polissacarídeos e temperatura, indicando a importância desses parâmetros para a manutenção da estabilidade operacional de um RBS com grânulos.

ABSTRACT Sequencing batch reactor (SBR) with aerobic granular biomass is a compact and promising technology in wastewater treatment. However, its use for sanitary sewage is still a challenge due to the instability and disintegration of the aggregates. The present work evaluated the biomass granulation in a pilot SBR, without addition of inoculum, for sanitary sewage treatment. The study was divided into three operational strategies with cycles composed by the phases of: filling, anoxic, aerobic, settling, effluent withdrawal and idle. The variations in the operational cycle time were: 4 hours (strategies I and II) and 6 hours (strategy III); and anoxic phase of 13, 30 and 90 minutes in strategies I, II and III, respectively. The granules development occurred in a natural way, without inoculation, and the reactor treated the sanitary wastewater meeting the national requirements of effluent discharge standards. The characteristics of the aerobic granular sludge and the reactor's performance improved with the anoxic phase increase. Granules (200-400 µm) were more than 80% of the biomass with good sedimentation characteristics (SVI30/SVI10 ratio between 0.7-1.0), in strategy III. The greatest relevance variables for the process were SVI30/SVI10 and COD Effluent/CODS Anoxic ratios, polysaccharides and temperature, indicating the importance of these parameters for the maintenance of the operational stability of granular SBR.

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A sequencing batch conventional membrane bioreactor (SB-CMBR) and sequencing batch hybrid membrane bioreactor (SB-HMBR) were operated in parallel under two different hydraulic retention times (HRTs) (namely 12 h and 6 h), and their chemical oxygen demand (COD) and nutrient removal performance, membrane fouling behavior, and microbial community characteristics were compared. Both systems exhibited high organic matter (> 95%) and ammonium (> 98%) removal performance regardless of the HRT applied. As the HRT was reduced from 12 to 6 h, total nitrogen removal slightly increased in both reactors, being higher in the carrier-based MBR, where anoxic zones may have been established within the biofilm. Conversely, total phosphorus removal improved only in the SB-CMBR at the shorter HRT. Moreover, activity batch assays have shown a faster P uptake rate in the SB-CMBR than in the SB-HMBR, a result likely associated with the lower relative abundance of phosphate-accumulating organisms in both adhered and suspended biomass fractions in the hybrid MBR. The results also revealed that more pronounced increases in the transmembrane pressure and, consequently, in the membrane fouling rate at higher COD loading rates were observed in the SB-CMBR, where the soluble microbial products (proteins, polysaccharides, and especially, transparent exopolymer particles), supernatant turbidity, and filamentous bacteria were more significant. Overall, as compared to the conventional MBR, the plastic media-based SB-HMBR showed a lower fouling propensity at all hydraulic conditions tested.

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RESUMO Este trabalho teve por objetivo produzir lodo granular aeróbio num reator em batelada sequencial não tubular, uma geometria diferente da usualmente utilizada nesses sistemas. Este reator foi inoculado com lodo ativado proveniente de uma estação de tratamento de esgoto municipal. O reator foi operado com ciclos de seis horas, com cinco horas de reação totalmente aeróbia. O efluente simulado continha um derivado de amido usado na indústria têxtil. A indução da granulação foi conseguida por meio da redução gradual do tempo de sedimentação, verificando-se que este é um parâmetro crítico do sistema. Após estabilização, com um tempo de sedimentação de 3 minutos, obteve-se um índice volumétrico de lodo de 25 mL.gSST-1, uma concentração de biomassa de 7 gSST.L-1 e uma eficiência de remoção da demanda química de oxigênio de 88%. Os grânulos obtidos foram armazenados úmidos durante 7 meses, a 4 e 25ºC, obtendo-se resultados excecionais na repartida dos reatores, com rápida recuperação das suas características de sedimentação, taxa de crescimento, estrutura e integridade granulares.

ABSTRACT This study aimed to produce aerobic granular sludge in a non-tubular sequencing batch reactor, which is an unusual geometry in these systems. This reactor was inoculated with activated sludge from a municipal wastewater treatment plant. The reactor was operated in cycles of six hours, with five hours of fully aerobic reaction. The simulated wastewater contained a starch derivative used in the textile industry. Granulation was induced by gradually reducing the settling time; therefore, this is a critical parameter of the system. After stabilization, with a sedimentation time of 3 minutes, a Sludge Volume Index after 30 minutes of settling of 25 mL.gSST-1, a biomass concentration of 7 gTSS.L-1 and a Chemical Oxygen Demand removal of 88% were obtained. The granules were stored wet for 7 months at 4 and 25ºC, yielding exceptional results in the re-start of the reactor, with rapid recovery of their sedimentation characteristics, growth rate, and granular structure and integrity.

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An electrocoagulation technique using a 3.5 L reactor, with aluminum electrodes in a monopolar arrangement with polarity switch at each 10 s was used to separate oil from synthetic oily water similar in oil concentration to produced water from offshore platforms. Up to 98% of oil removal was achieved after 20 min of processing. Processing time dependence of the oil removal and pH was measured and successfully adjusted to exponential models, indicating a pseudo first order behavior. Statistical analysis was used to prove that electrical conductivity and total solids depend significantly on the concentration of electrolyte (NaCl) in the medium. Oil removal depends mostly on the distance between the electrodes but is proportional to electrolyte concentration when initial pH is 8. Electrocoagulation with polarity switch maximizes the lifetime of the electrodes. The process reduced oil concentration to a value below that stipulated by law, proving it can be an efficient technology to minimize the offshore drilling impact in the environment.

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Methane is produced in anaerobic environments, such as reactors used to treat wastewaters, and can be consumed by methanotrophs. The composition and structure of a microbial community enriched from anaerobic sewage sludge under methane-oxidation condition coupled to denitrification were investigated. Denaturing gradient gel electrophoresis (DGGE) analysis retrieved sequences of Methylocaldum and Chloroflexi. Deep sequencing analysis revealed a complex community that changed over time and was affected by methane concentration. Methylocaldum (8.2%), Methylosinus (2.3%), Methylomonas (0.02%), Methylacidiphilales (0.45%), Nitrospirales (0.18%), and Methanosarcinales (0.3%) were detected. Despite denitrifying conditions provided, Nitrospirales and Methanosarcinales, known to perform anaerobic methane oxidation coupled to denitrification (DAMO) process, were in very low abundance. Results demonstrated that aerobic and anaerobic methanotrophs coexisted in the reactor together with heterotrophic microorganisms, suggesting that a diverse microbial community was important to sustain methanotrophic activity. The methanogenic sludge was a good inoculum to enrich methanotrophs, and cultivation conditions play a selective role in determining community composition.

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